This invention relates to a wellhead assembly and method of operation and, more particularly, to a wellhead assembly which accepts a downhole tool run on a wireline within an injection bore in which the wireline is protected from the flow of the injected fluid at the injection port, but which does not interfere with an isolation valve in the injection bore and provides for convenient removal or change of downhole tools.
Many downhole tools have been developed in recent years for performing tasks within pipe strings of formations from the end of a wireline. However, problems develop when the application requires that such downhole tools monitor conditions or otherwise perform tasks while fluid is injected into the bore containing the wireline and downhole tool. The fluid flows transverse to the wireline at the injection port where it enters the injection bore and subjects the wireline to potentially serious vibration and erosion.
The prior art has addressed these problems by threading the wireline through a strong, rigid cable protector or stinger which covers the wireline in the immediate vicinity of the injection port. However, the stinger of the prior art is deployed through an isolation valve and renders the isolation valve inoperative, whereby seriously compromising the safety of operations at the well. Further, the inoperative isolation valve forces operations requiring insertion, removal or replacement of the downhole tool to be performed at atmospheric pressure. However, there are other safety concerns in steps necessary to reduce the pressure. In addition, such depressurization steps are inconvenient, often counterproductive to the purposes of the injection well and sometimes seriously damaging to downhole operations.